Stacking subs

For years I’ve used a pair of Velodyne HGS-15s placed in the front corners. They are acoustically corrected by a bass manager and seem to integrate flawlessly with the KEF Reference 1s. In a recent post, auxinput suggested I replace the HGS-15s with HGS-10s for LF extension of the KEFs and use the HGS-15s with LFE from the Bryston SP3. That seems like a fine suggestion. I wonder about stacking the HGS-10s in the corners atop the HGS-15s, the easiest and neatest solution. Any thoughts or advice would be appreciated.